Can overlay dynamic text / teletext on video?

[c2h2]

Hi, guys, Im trying to overlay some dynamic text/subtitle/teletext to the screen of my stream viewers or VOD viewers. for example, student in a class all viewing a stream, and i would like to broadcast a message, that "class is over soon". preferably this is text can be provided from http, say http://lectureServer/teletext.txt

I have tried:
--marq-marquee=<string> and also tryid http://www.recipester.org/q:video%20dyn ... 0add%20vlc
But it doesn't support text.

I have also looked thoroughly the command line manual, havent found the answer.

Hopefully someone has done it can point me some directions, thanks!